Processed meat products, such as bologna, hot dogs, sausages, and whole muscle products including ham and turkey, among many others, are convenient and popular food items. A variety of commercial systems are available for making certain processed meats. In one type of commercial system used for making processed meat products including bologna and hot dogs, raw meat in the form of chunks or pieces and other ingredients such as spices are ground, chopped and/or otherwise blended with one or more salt solutions or brine to provide a mixture that can subsequently be formed into a stable meat emulsion or protein matrix. Similar steps of grinding, chopping and/or otherwise working are also employed in making coarse ground products such as sausages, whole muscle products such as processed ham and processed turkey and other processed meats. In each case, proteins form a matrix to hold or bond the separate meat pieces together.
A stable protein matrix requires the protein bonds to suspend or bond with fat and water. Creation of protein bonds in this context requires a process commonly known as protein extraction. In this process, salt soluble or salt extractable, heat coagulable proteins such as myosin, actomyosin, and actin bind water, swell and become tacky as a result of working or blending of the meat in the presence of a salt or a salt solution. The proteins are subsequently set when heated to create a bond. Other myofibrillar proteins, as well as sarcoplasmic or water soluble or extractable proteins, may also play a role in bonding. Salt solutions that may be used in protein extraction include, but are not limited to, sodium chloride, sodium pyrophosphate or diphosphate, potassium chloride, sodium lactate, and potassium lactate. In protein extraction as described herein, the mechanism believed to be primary responsible for the creation of the bonds involves binding proteins, salts, fats, and/or water and subsequent swelling of the proteins, rather than solution of the proteins. More precisely, it is believed that the salt solution frees bonding sites on the proteins for bonding with each other, as well as with water and fat.
Batch processes for blending meat and other ingredients and extracting protein are well known. A known method for achieving protein extraction and ingredient blending for certain products such as whole muscle meats including processed turkey and processed ham involves puncturing the whole muscle meat with hypodermic-type needles, injecting brine or salt solution through the needles, and using a batch processor or mixer to work the meat for approximately 45 minutes under vacuum conditions to remove air, as discussed below. For other products such as coarse ground meat including sausages and emulsified products, meat is ground and added to a batch processor with water, salt solution, spices, and/or other ingredients and worked with or without a vacuum for up to an hour, or in one approach, for 15 to 45 minutes.
A large batch mixer may process approximately 6,000 to 12,000 pounds per hour. The meat product constituents including the meats and the additives are combined in the low shear batch mixer for whole muscle products. This mixing stage typically requires 30 to 60 minutes of being mixed. It is during this time that the constituents are transformed into a mixture that will form a stable protein matrix.
A stable protein matrix is formed when mixtures for whole muscle products, coarse ground products, and emulsified products allow the salt solution to reach the salt-extractable protein. The time it takes for the salt to reach the salt-extractable protein may vary and it is desirable to decrease the time it takes for the process to occur. This process, known as curing, achieves the protein extraction. For whole muscle products, delivery of the brine solution through injection of the hypodermic-type needles inserted into the meat chunks is a relatively imprecise method for attempting to reduce the distance through which the salt solution must diffuse. The curing stage typically requires 24-48 hours for satisfactory diffusion, and the batches are stored in vats and placed into coolers for the cure time. Once the protein extraction has occurred, the mixture may then be further processed.
With respect to the processing equipment, while such mixers have been used commercially for many years, they have significant drawbacks with respect to their space requirements and cost due to their large size, as well as the length of time required for processing each batch, and the time and expense associated with cleaning of the apparatus.
As for the process, conventional batch processing is a lengthy process requiring a number of discrete steps. Initially, various meats are provided by a vendor with specified contents. More specifically, the meats are provided with a specified protein, fat, and/or water content, typically a percentage by weight. A batch sheet is provided to processing plant personnel indicating what mixture of meats, water, and additives are to be combined for one of a variety of meat products. In addition, the batch sheet often needs to be adjusted or more precisely indicated after the batch of meat has arrived at the plant. Based on the formula desired for the final meat product, the plant personnel often have to adjust the meats selected for processing in a particular batch. The final product mixture is carefully controlled. If a particular meat is utilized where the fat content is greater than what the batch sheet calls for, the final product may have an excessive amount of fat. To avoid this, the plant personnel would increase the protein provided by other meats to balance the fat content.
Unfortunately, this is not necessarily a sufficiently precise approach. Each meat, as well as each chunk in a batch of meat, may vary significantly from a sample taken and assumed to be average. Once the water and other additives are mixed in with the batch, it may be difficult to alter the balance. At times, the resulting batch is determined to be inaccurately mixed, and remedial procedures must be taken such as mixing the batch in with additional correction materials. In order to reduce the likelihood of an imprecise batch, relatively large quantities of meat are provided for a single batch in hopes of minimizing or driving to a mean the composition deviation resulting from a meat portion with an aberrational content. A typical amount of a particular meat for a batch is approximately 2000 lbs.
Input constituents are calculated to result in a specific quantity of cooked product. If excessive water or fat is lost post-mix such as during the cook stage, the carefully regulated water, fat, and meat ratios will be off-target. If fat is lost prior to the cook stage, it often remains in the machinery or piping through which the mixture is processed. This can result in down time for the machinery, likelihood of damaged machinery, and greater labor in cleaning the machinery. Furthermore, cooked emulsified products rely, to some degree, on non-protein or non-bound materials to provide the proper texture. The proteins bind to form a matrix with each other and, in the absence of sufficient fat or water, these bonds may form a larger, stronger matrix, which leads the product to become somewhat rubbery. Conversely, if there is too much water, the cooked product may be too soft, and may lack integrity.
As used herein, the term additives may refer broadly to brine solution, water without salt, a spice slurry, nitrite, or other additives. Though the brine solution and the meats themselves each include water, the balance for the final product is typically adjusted with a quantity of water. The spice slurry provides, for instance, flavorings and water. One additive is typically nitrite which is used as a preservative and to provide a desired color. Other inert additives, such as corn starch or non-functional proteins, may also be included.
As the mixture constituents are churned in the mixer for up to an hour, contact with air may produce a froth on the surface of the meat pieces. A final product having visible air may be unacceptable. In some cases, the product must be reprocessed and mixed in with subsequent batches. Air in the product may appear as surface bubbles, or as surface holes. Entrapped air may also lead to product swelling during cooking or may lead to the product having visible air bubbles within its interior.
Air affects the product in other ways as well. For instance, some proteins are denatured by the presence of air, which reduces the functionality of the meat for binding fat and water. The air can also react with the nitrite to retard the development of the proper color. The resulting color may then be undesirable or objectionable to consumers.
To avoid being stirred into the mixture, vacuum pressure may be applied during the mixing process. This requires an extensive set up including the vacuum itself and seals to maintain the pressure. The vacuum system and seals require maintenance, and occasionally leak which results in downgraded product.
While such mixers have been used commercially for many years, they have significant drawbacks. For example, one of the problems is that air may undesirably be drawn into the product. Other drawbacks for the mixers include their space requirements and cost due to their large size, labor costs, the length of time required for processing each batch, vat handling and transfer yield loss, and the time and expense associated with cleaning of the apparatus.
In addition to the problems encountered with batch mixers for both whole muscle products and emulsified products, there are additional constraints for mixers that process whole muscle products. For example, in reducing the time required for processing and accelerating the formation of a stable meat mixture, the meat chunks introduced into the mixer may be subject to increased shear forces. However, high shear forces may not only distort the shape of size of the meat pieces but also impact the texture, mouth feel, and appearance of the meat after processing. Thus, in an effort to speed-up the processing of whole meat products, the processes cannot subject the whole meat to excessive shear force.